View Full Version : Yamaha CR-240.....No Output


sweatyk
05-19-2012, 10:12 AM
Just got this receiver and everything lights up, I'm getting FM signal but no sound thru any of the speaker outputs on either channel and nothing thru the headphones. I have deoxed the volume pot and all solder joints look good.I have also checked and deoxed the tape monitor switch.Any suggestions of where else to look?
If it was in one channel only I would suspect the output chip but I don't think that could be it. Unless both went out at the same time. I was trying to find a service manual so I could trace the voltages but all I could fine was the owners with the one schematic. I would love to get this up and running to use it out in my garage.

avionic
05-19-2012, 11:45 AM
If you don't hear a relay "click" shortly after power on.Then it probably has a bad output chip.If you do hear the relay, try cleaning your speaker select switch.

sweatyk
05-19-2012, 11:58 AM
Could the relay itself be bad? And if so how to test it?

ryuuoh
05-19-2012, 12:49 PM
With those power pack amps, it's usually the pack that packs up. See this thread for possible replacements:
http://www.audiokarma.org/forums/showthread.php?t=369441

sweatyk
05-19-2012, 02:02 PM
So I'm guessing that the originals are next to impossible to find and the STK078G is a good replacement that works the same in it's place?

sweatyk
05-19-2012, 02:03 PM
Well if nothing else the speaker selector switch was just dismantled and got a complete and thorough cleaning and lube job.....lol

ryuuoh
05-19-2012, 03:24 PM
Per Merrylander, it's the proper part.
Available here:
http://www.bdent.com/STK078G-p/stk078g.htm

sweatyk
05-19-2012, 07:47 PM
Testing has confirmed it is one of the output chips...

Thanks Avionic!!!!

sweatyk
05-19-2012, 07:49 PM
Per Merrylander, it's the proper part.
Available here:
http://www.bdent.com/STK078G-p/stk078g.htm

And thanks for the link for the part!!!:wave::beerchug:

petehall347
05-19-2012, 07:55 PM
there may or may not be some resistors that need checking before replacing the power pack .. it could be detrimental to the new one if out of tolerance .

sweatyk
05-19-2012, 08:24 PM
there may or may not be some resistors that need checking before replacing the power pack .. it could be detrimental to the new one if out of tolerance .


Thanks....I will keep that in mind when I go to replace it.

sweatyk
05-21-2012, 06:21 PM
Well I decided to poke around the circuit of this output chip and found some shorted diodes. The owners manual has a basic schematic but no parts list and these diodes have no markings on them. Does anyone have a link to or a parts list for this model?

petehall347
05-21-2012, 06:36 PM
think i found it ..cant remember if you need to sign up .. don't think so though ..it can be a long wait waiting for the link bottom right .. refresh if nothing after 15 mins or so ..
http://elektrotanya.com/yamaha_cr240.pdf/download.html
or easier is here on ak .. i think ..http://akdatabase.org/AKview/thumbnails.php?album=3&page=5
schem is in owners manual ..did you test diodes out of circuit ? if not do it
diodes will/should have marks indicating the values . you may need a magnifying glass to read them

sweatyk
05-21-2012, 07:20 PM
I have the owners manual with the schematic and it does not indicate what the diodes are. That's why I was looking for a parts list. To answer your other questions, yes I tested them out of the circuit. And I have also looked at them with a magnifying glass and neither have any markings on them. If they did at one time they are certainly gone now.........

petehall347
05-21-2012, 07:25 PM
if you can post a good picture of the diodes please do so .. it may help in subs for them
its late on for me but if you look up the data sheets for the output chips there is often a suggested circuit for them and may indicate the correct diodes to use ..

sweatyk
05-21-2012, 07:56 PM
Let me see what I can do....if you have a schematic to look at they come off of pin 5 and 9 of the chip. I will post a pic soon. Thanks

sweatyk
05-21-2012, 08:17 PM
This is the best pic I could get with my camera....

http://i449.photobucket.com/albums/qq211/sweatyk702/stuff.jpg

ryuuoh
05-21-2012, 09:14 PM
Try a pic with a coin next to it for context. A guess would be a 4148 diode or similar. Could be a zener diode too.

sweatyk
05-21-2012, 09:24 PM
I contacted Yamaha and will speak with them tomorrow about a service manual. They claim to have it on CD and that i can purchase it from them. When I call them I will make sure that it comes with a parts list otherwise it will not help me in this matter. I will see what I can do about another pic tomorrow evening.

avionic
05-21-2012, 11:09 PM
Do these bad diodes have a reference # like D102 or D301 etc.Theres quite a few diodes in that unit.
---nevermind---
There not zeners.Probably get by with 1N4148's.

sweatyk
05-22-2012, 04:36 AM
D301 & d303

sweatyk
05-22-2012, 11:50 AM
Well Yamaha was of no help. They had nothing in their archives for a parts list or a service manual......oh well it was worth a try. Saw one on Ebay. Waiting to here from them to see if the parts list is included before I purchase it.

sweatyk
05-22-2012, 01:35 PM
Scored the service manual on fleebay!!!!

sweatyk
05-24-2012, 05:20 PM
OK the service manual is in!....according to the parts list the diodes are a is1555 or can interchange with a is2473. Looks like I have some searching to do.

sweatyk
05-24-2012, 05:25 PM
Try a pic with a coin next to it for context. A guess would be a 4148 diode or similar. Could be a zener diode too.

After doing a cross reference it looks like your guess was correct....1n4148 should sub for the original. And I happen to have a whole pack of them from Rat Shack.....woohoo

petehall347
05-24-2012, 05:28 PM
i think its 1s not is ...rectifier / detector diode .
in this application avionic should be correct . with the rectifier diode sub

sweatyk
05-24-2012, 06:14 PM
i think its 1s not is ...rectifier / detector diode .
in this application avionic should be correct . with the rectifier diode sub
Believe it or not it is an "i" in the service manual parts list.....I had to do a double take but that is it. Not that it matters of course. Just glad to find out what will work in it's place!!!!!

sweatyk
05-29-2012, 05:19 PM
Well here's an update of where I'm at right now. The power module came in today so I removed the heat shield and with both modules off I cleaned the old heat compound off. Installed both the new and the old good one back to the heat shield. As I was inspecting the area near there on the PCB I noticed a leaking cap. So I have decided while it was tore down to replace all of the electrolytic caps associated with both channels near where they mount. The picture shows the one side I have removed and on the far right you can see the dark spot on the PCB where the cap was leaking. I'm leaving the ones on the left in for reference so I will know which go where. Kinda like removing all of the spark plugs wires from your car at one time then cant remember the order they go back on....lol. Of course the local "Rat Shack" did not have all of what I needed so it's off to Mouser for the caps. So until then I guess I'm on hold with putting this thing back together. Just wanted to share the progress.

http://i449.photobucket.com/albums/qq211/sweatyk702/stuff052.jpg

http://i449.photobucket.com/albums/qq211/sweatyk702/stuff053.jpg

sweatyk
06-01-2012, 04:10 PM
Here's the latest. Replaced the caps as you can see in the pic. Replace 2 shorted diodes, and one of the output modules. And....................we have sound! I was using headphones and was receiving both channels however when I turn it to full right channel there is a hum in the background. I still plan to deox everything again but this could be something else. I thought I had got all of the caps from each channel but could have overlooked something.

http://i449.photobucket.com/albums/qq211/sweatyk702/stuff059.jpg

sweatyk
06-02-2012, 01:45 PM
Final chapter. Deoxed all controls, all the bulbs are lit, full strength FM signal, and it sounds very nice and warm. Haven't tried tape or phono yet seeing how I do not have these things to run through it. However I feel that it should work properly and I will find out very soon so consider this thread DONE! Thank you to all that commented and helped. Especially Avionic.......thanks again.